Why Does the Hot Water in Your Everett Home Smell Like Rotten Eggs?

Most people who call us about a rotten egg smell in their hot water have already poured something down the drain. Sometimes twice.

It’s the reasonable guess. You’re at a sink, so the smell must be at the sink. Except it comes back within a day, only turns up when the tap runs, and is worst in the shower, which is not how a drain behaves. Drain smell sits in a room whether the water is on or not.

Read this part first if what you’re smelling might be gas

They’re described the same way and they are not the same thing. Water heater sulfur arrives when you run a tap, from the water. Natural gas odorant is in the air, doesn’t need a tap running, and is strongest near an appliance or a gas line. If you smell rotten eggs in the air with no water running, treat it as gas: get everyone out of the house first and call from outside.

That’s the whole safety fork. Everything below is about the quieter version, a smell that only shows up at the hot tap and never behaves like a gas leak at all.

There’s no single test, and here’s why

Hot side only means hydrogen sulfide is forming inside your tank. Bacteria that feed on sulfur (harmless in themselves, and present in plenty of water supplies) meet the sacrificial metal rod that sits in there protecting the tank from rust, and the by-product smells like a bad egg. Not sewage backing up. Not a gas leak. In a normal residential tank it’s a nuisance rather than a hazard, and the repair is some combination of flushing, sanitising, and swapping the rod for a different kind.

Inside almost every tank water heater there’s a long metal rod hanging down into the water, usually magnesium. It’s a sacrificial anode, and the name is the whole explanation: it corrodes instead of your tank. That rod giving itself up is the cheapest reason a water heater lasts as long as it does.

Here’s the catch. As the magnesium breaks down it sheds electrons into the water, and sulfate-reducing bacteria will happily take them. The by-product is hydrogen sulfide. So the smell isn’t a sign the rod failed. It’s a sign the rod is doing exactly what it was installed to do, in water that happens to have the wrong company in it.

Which is also why it’s the hot tap and not the cold. A tank is warm, dark and low on oxygen, and those bacteria like all three. Your cold lines are none of that, and have no rod in them. Same reason a tankless unit rarely produces this: no tank, no rod, nothing standing still.

So how can you tell where it’s actually coming from?

The signs, roughly in the order they point somewhere different:

• Hot tap only. The problem is inside your water heater, and that’s the outcome by a wide margin.
• Hot and cold, both. The tank is off the hook. Something upstream is carrying the odour in: the supply itself, an overdue filter cartridge, or a softener nobody has serviced since the previous owner installed it.
• One fixture, and only one fixture. That’s usually a gunked-up aerator, or a branch line to a bathroom used twice a year where water sits long enough to go stale.

Checks you can do yourself this afternoon

There’s a test that takes ninety seconds and settles the whole thing.

Fill a glass from a cold tap and carry it into another room, away from the sink and the drain, before you smell it. Do the same with a glass of hot. If it’s the one-fixture case, run that tap hard for a few minutes and see whether it clears.

When to call a licensed plumber

Where we’d tell you to stop and call: the rod is seized. Common on older tanks and anything crammed into a closet with no clearance above it. Getting one out in one piece takes real torque and room to swing, and rounding off a stuck anode makes the job worse.

The version that changes the urgency is a smell on the cold side of a private well. That’s no longer a water heater conversation, and it deserves a proper water test before anyone starts replacing parts. Snohomish County residents relying on a private well can get their drinking water tested for hydrogen sulfide, and it’s worth doing before you assume rotten eggs at the tap means the tank is guilty.

How we handle a rotten egg smell call

Start cheap, escalate only if you need to.

• Flush the tank first. Drain water off the bottom until it runs clean. Sediment is where the bacteria hide, and skipping this makes everything after it less effective.
• Then sanitise it. A peroxide treatment run through the tank and flushed back out knocks the population down. This is where we’d stop the DIY for most people, since putting chemicals into your own potable water is easy to get wrong.
• Change the anode last, because it’s the fix that sticks. An aluminium-zinc rod instead of magnesium usually ends it. A powered anode, which protects the tank electrically and sacrifices no metal at all, ends it more permanently for more money up front.

There’s also the temperature lever. State health department guidance on sulfur bacteria calls for raising the tank thermostat to 160°F and holding it there for about eight hours, since the bacteria die off above 140°F, then flushing the tank to clear out what’s left. Confirm the tank has a working pressure relief valve before doing this. It works, and it’s the fastest fix on this list. Two cautions: it raises scald risk at every tap in the house, which matters a great deal with kids or older adults and no mixing valve on the outlet, and it isn’t a setting to leave changed.

Snohomish County homes don’t all get this the same way

We don’t get this call evenly across the map. Two setups account for most of them.

The first is a house on a private well, out past the city limits, in the unincorporated parts of the county where a well was cheaper than running a line. Groundwater is where the sulfur usually comes from. Most Everett addresses are on municipal supply and we see this far less often on city water, though “less often” isn’t “never”: we’ve pulled some ripe rods out of tanks on the north end.

The second has nothing to do with the water and everything to do with the calendar. Tanks that sit still go bad-smelling. A week away in August, a rental between tenants, a mother-in-law unit empty half the year. Water stops moving, stays warm, and the bacteria get an uninterrupted run at it. We take a lot of these calls the Monday after people come home from vacation.

Long shot, but check it anyway: if a previous owner left a water softener in the garage, put it on the list. They’re a classic contributor, and less common here than in hard-water regions, which is exactly why nobody has thought about the thing in years.

Can you shower in it? Can you drink it?

Shower: yes, in the ordinary case. At the concentrations that come out of a home water heater this is an odour problem, and plenty of people live with it for months before calling anyone. That said, we’re plumbers and not the health department. If anyone in the house is genuinely reacting to it, get the water tested.

Drinking has an easier answer: don’t drink from the hot tap regardless. True in every house, smell or no smell, and nothing to do with sulfur. Use the cold side.

What that hydrogen sulfide odor complaint means for your health

The rotten egg smell is hydrogen sulfide gas, and public health agencies have real data on hydrogen sulfide health effects at different exposure levels, not just the concentrations found in industrial settings. The federal Agency for Toxic Substances and Disease Registry publishes guidance on exactly this, and the short version is reassuring for a strong rotten-egg odor coming out of a water heater: people aren’t likely to have health effects at typical environmental exposure levels, and the exposure levels involved in ordinary household odor complaints sit far below the levels where the agency starts flagging respiratory or nervous system effects. Those effects generally show up at levels at least 100 times higher than typical background levels, the kind you’d find in an occupational setting, not a bathroom.

Eye, nose, and throat irritation from hydrogen sulfide is a long-term, higher-level effect, not something that shows up from a characteristic rotten egg smell drifting out of a shower for ten minutes. That distinction matters, because a “my water smells like rotten eggs” complaint online often gets treated like a public health emergency, when the actual health data doesn’t support that. It isn’t nothing. Long-term exposure at a level you can consistently smell is still worth addressing. But the exposure in an ordinary residential sulfur smell case is a long way from rotten eggs turning into an actual health hazard.

Where public health guidance gets more serious is occupational exposure, like refineries and sewage systems, where hydrogen sulfide can build up to levels high enough to cause loss of consciousness. A county health inspector or a water-testing lab can confirm the actual health numbers if you want them, but for most homes on the municipal system, this stays a comfort problem rather than anything that needs the health department’s attention.

A few pages on our site that go deeper

More information on each of these, if you want to go deeper on a specific service:

• Water heater repair and replacement
• Everett tankless specialists
• Emergency plumbing team, if it turns out to be gas instead of sulfur
• Everett residential plumbing

A few more habits worth keeping

Most of this smell is preventable with a little routine attention rather than a call once a year. A tank that gets flushed on a schedule and an anode that’s the right metal for your water rarely gets the chance to build up enough bacteria to notice.

A quick checklist for a healthy water heater

• Flush the tank at least once a year. Sediment is where the bacteria hide.
• Know whether your tank runs a magnesium or an aluminium-zinc anode, and which one your water actually tolerates.
• Confirm the pressure relief valve works before ever raising the tank’s temperature setting.
• Reset the thermostat after any high-temperature treatment. Leaving it there is a scald risk, not a fix.
• If a previous owner left a water softener in the garage, find out if it’s still working, or still there at all.

Questions people ask us after the flush

Why is it worse after we’ve been away for a week?

Because the water stopped moving. Fresh water coming in keeps a tank stirred and diluted; a still tank at a comfortable temperature is close to ideal for the bacteria involved. Turning the heater to its vacation setting before you go helps, and running the hot taps hard for a few minutes when you get back clears a surprising amount of it.

It started right after we got a new water heater. Is it defective?

No, and this catches people out. A new tank comes with a fresh magnesium anode, far more reactive than the worn-down stub in the old unit. If your water carries the bacteria, that new rod produces more hydrogen sulfide than the old one did. The tank is fine. It’s the wrong rod for your water, and usually a straightforward swap.

Is this the same smell as a gas leak?

They’re described the same way and they are not the same thing. Water heater sulfur arrives when you run a tap, from the water. Natural gas odorant is in the air, doesn’t need a tap running, and is strongest near an appliance or a gas line. If you smell rotten eggs in the air with no water running, treat it as gas: get everyone out of the house first and call from outside.

Will a filter or a softener take care of it?

Not if the smell is forming in the tank, which is the usual case. Filtration ahead of the heater can’t touch a reaction happening downstream of it. Treatment gear is the right answer when the odour is in the incoming water, mostly a well situation, and it should be specified off an actual water test rather than guesswork.

Can I just leave the thermostat turned up?

We’d rather you didn’t. It’s a treatment, not a setting. Leaving it there raises scald risk at every fixture, works the tank harder, and doesn’t address the rod that’s feeding the problem. Use it to reset the situation, then bring it back and fix the actual cause.

How long before it comes back?

If all you did was flush and sanitise, expect it back within weeks or months, depending on your water and how much the house gets used. That’s not a failure, just the nature of a treatment that doesn’t change the conditions. Change the anode and most homes are done with it for the life of the tank.